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Aminoaciduria

Definition

Aminoaciduria is an abnormal amount of amino acids in the urine. Amino acids are the building blocks for proteins in the body.

This article discusses the test used to look for increased amounts of amino acids in the urine.

See also:

• Amino acids blood test
• Inborn errors of metabolism

Alternative Names

Amino acids - urine; Urine amino acids

How the test is performed

A clean-catch urine sample is needed. This is often done at your doctor's office or health clinic.

How to prepare for the test

No special preparations are necessary. Make sure your doctor knows about all the medicines you or your child are taking or have recently used. If this test is being done on an infant who is breast-feeding, make sure the health care provider knows what medicines the nursing mother is taking.

How the test will feel

The test involves only normal urination.

Why the test is performed

This test is done to measure amino acid levels in the urine. There are many different types of amino acids. It is common for some of each kind to be found in the urine, but increased levels of individual amino acids can be a sign of an inborn error of metabolism.

Normal Values

The specific value is measured in micromoles per deciliter (micromol/dL).

• Alanine
  • Children: 65 to 190
  • Adults: 160 to 690
• Alpha-aminoadipic acid
  • Children: 25 to 78
  • Adults: 0 to 165
• Alpha-amino-N-butyric acid
  • Children: 7 to 25
  • Adults: 0 to 28
• Arginine
  • Children: 10 to 25
  • Adults: 13 to 64
• Asparagine
  • Children: 15 to 40
  • Adults: 34 to 100
• Aspartic acid
  • Children: 10 to 26
  • Adults: 14 to 89
• Beta-alanine
  • Children: 0 to 42
  • Adults: 0 to 93
• Beta-amino-isobutyric acid
  • Children: 25 to 96
  • Adults: 10 to 235
• Carnosine
  • Children: 34 to 220
  • Adults: 16 to 125
• Citrulline
  • Children: 0 to 13
  • Adults: 0 to 11
• Cystine
  • Children: 11 to 53
  • Adults: 28 to 115
• Glutamic acid
  • Children: 13 to 22
  • Adults: 27 to 105
• Glutamine
  • Children: 150 to 400
  • Adults: 300 to 1,040
• Glycine
  • Children: 195 to 855
  • Adults: 750 to 2,400
• Histidine
  • Children: 46 to 725
  • Adults: 500 to 1,500
• Hydroxyproline
  • Children: not measured
  • Adults: not measured
• Isoleucine
  • Children: 3 to 15
  • Adults: 4 to 23
• Leucine
  • Children: 9 to 23
  • Adults: 20 to 77
• Lysine
  • Children: 19 to 140
  • Adults: 32 to 290
• Methionine
  • Children: 7 to 20
  • Adults: 5 to 30
• 1-methylhistidine
  • Children: 41 to 300
  • Adults: 68 to 855
• 3-methylhistidine
  • Children: 42 to 135
  • Adults: 64 to 320
• Ornithine
  • Children: 3 to 16
  • Adults: 5 to 70
• Phenylalanine
  • Children: 20 to 61
  • Adults: 36 to 90
• Phosphoserine
  • Children: 16 to 34
  • Adults: 28 to 95
• Phosphoethanolamine
  • Children: 24 to 66
  • Adults: 17 to 95
• Proline
  • Children: not measured
  • Adults: not measured
• Serine
  • Children: 93 to 210
  • Adults: 200 to 695
• Taurine
  • Children: 62 to 970
  • Adults: 267 to 1,290
• Threonine
  • Children: 25 to 100
  • Adults: 80 to 320
• Tyrosine
  • Children: 30 to 83
  • Adults: 38 to 145
• Valine
  • Children: 17 to 37
  • Adults: 19 to 74

What abnormal results mean

Increased total urine amino acids may be due to:

• Alkaptonuria
• Canavan disease
• Cystinosis
• Cystathioninuria
• Fructose intolerance
• Galactosemia
• Hartnup disease
• Homocystinuria
• Hyperammonemia
• Hyperparathyroidism
• Maple syrup urine disease
• Methylmalonic acidemia
• Multiple myeloma
• Ornithine transcarbamylase deficiency
• Osteomalacia
• Propionic acidemia
• Rickets
• Tyrosinemia type 1
• Tyrosinemia type 2
• Viral hepatitis
• Wilson's disease

Special considerations

Failure to have the urine sample promptly evaluated in the laboratory alters the results of the test.

This test is ineffective if the baby is under 6 weeks old and has not been fed dietary protein in the last 48 hours.

Urine chromatography is necessary to accurately measure increased levels of specific amino acids.

Screening infants for increased levels of amino acids can lead to early diagnosis of an inborn error of metabolism. If the condition is promptly treated, complications such as severe mental retardation may be prevented.